Vacations at the shore during childhood may boost the risk of the deadly skin cancer melanoma later in life, a new study suggests. Researchers from Denver evaluated 681 children born in 1998 in Colorado, asking their parents about childhood vacation destinations and then conducting skin exams when the children were age 7 to look for nevi, commonly known as moles. These moles are a risk factor for developing malignant melanoma, the most deadly form of skin cancer. "Moles went up 5% for every vacation they took [beginning at age 1 year]," said study senior author Lori Crane, an associate professor and chairwoman of community and behavioral health at the Colorado School of Public Health.

The American Cancer Society estimates there will be about 62,500 new cases of melanoma in 2008, and about 8,400 deaths. Crane said that, while daily sun exposure at home wasn't found to be related to the number of moles that developed on the children, there was a link to the number of vacations by the water. And the moles seemed to increase despite sunscreen use. "Ninety percent said they used sunscreen most or all of the time," she said.

Crane, like other experts, said parents often believe sunscreen is a safeguard against skin cancer. While sunscreen does offer some protection, children who wear it may stay out in the sun longer—long after the protection from the sunscreen has subsided, she said.

Another skin cancer expert said the new study confirms what many dermatologists have long known—that increased sun exposure, especially intermittent exposure in childhood, increases the risk of melanoma later in life. While other skin cancers, such as squamous cell, are linked to cumulative sun exposure, "for melanoma, the story is a little more muddled," said Dr. Clifford Perlis, director of MOHS and dermatologic surgery at Fox Chase Cancer Center in Philadelphia. "It's not always linked to cumulative exposure, but to intermittent. The reasons are not clear."

"What this study does support is what we have been saying for a long time—limit sun exposure during peak hours. Wear protective clothing," Perlis said. Sunscreen is also advised.

The message of the study isn't to stop taking beach vacations, Perlis said. There are "lots of healthy things" about them, he said. Crane's suggestion is more strident. She advises parents to skip or curtail waterside vacations when their children are young. "Wait until the kid is 10 or 12," she said.

When parents do take children to the beach, they should be cautious, Crane said. "They should not rely just on sunscreen. They should get water shirts for their kids. They should try to avoid middle-of-the-day outside activities," she said. Better yet, avoid outdoor activities between 10 a.m. and 4 p.m., when the sun's ultraviolet rays are strongest.

The study was published in the February issue of Cancer Epidemiology, Biomarkers & Prevention.